Radio Frequency Spectra of 388 Bright 74 MHz Sources

TL;DR

This paper compiles and improves radio frequency spectra for bright 74 MHz sources using VLSS data, providing a valuable resource for low frequency radio astronomy calibration.

Contribution

It presents a comprehensive, corrected spectral database for bright radio sources at 74 MHz, enhancing previous efforts with more reliable data and broader sky coverage.

Findings

Spectra for all sources brighter than 15 Jy at 74 MHz are compiled.

Spectral shape parameters are derived and made available.

The dataset improves calibration for current and future low frequency radio observations.

Abstract

As a service to the community, we have compiled radio frequency spectra from the literature for all sources within the VLA Low Frequency Sky Survey (VLSS) that are brighter than 15 Jy at 74 MHz. Over 160 references were used to maximize the amount of spectral data used in the compilation of the spectra, while also taking care to determine the corrections needed to put the flux densities from all reference on the same absolute flux density scale. With the new VLSS data, we are able to vastly improve upon previous efforts to compile spectra of bright radio sources to frequencies below 100 MHz because (1) the VLSS flux densities are more reliable than those from some previous low frequency surveys and (2) the VLSS covers a much larger area of the sky (declination >-30 deg.) than many other low frequency surveys (e.g., the 8C survey). In this paper, we discuss how the spectra were constructed and how parameters quantifying the shapes of the spectra were derived. Both the spectra and the shape parameters are made available here to assist in the calibration of observations made with current and future low frequency radio facilities.